The present invention relates to a washing agent dispenser for a household washing machine, namely a dishwasher and to a household washing machine using such a washing agent dispenser, as well as to a visual signalling device for such a washing agent dispenser and to an assembly method for such a visual signalling device.
As known, washing machines are usually equipped with a washing agent dispenser, meant as powder and/or liquid detergents and washing aids; typically, the latter consisting of softening media for laundry washing machines and rinsing aids for dishwashing machines.
In the instance of a dishwasher, washing agent dispensers usually comprise a body made from plastic material partially built-in on the machine inner-door, i.e. the side of the machine front loading door facing inside the wash tub.
The above body has a recess for containing a detergent, usually in powder form, which has a small tilting or sliding cover; opening of this cover is appropriately controlled by a machine programmer or timer.
A tank is also provided within the dispenser body, for containing a second liquid washing agent, typically a rinsing aid; usually, the amount of rinsing aid that can be loaded in the above tank, which is fitted with a proper plug, is sufficient for performing several wash cycles.
Typically, the dispenser has inside a small chamber being associated to the above tank, which is used for dosing the amount of rinsing aid to be released during a wash cycle; in particular, the rinsing-aid dosing system exploits the opening-closing movement of the machine door, i.e. horizontal in its open position and vertical in its closed position, for loading some rinsing aid from the tank to the dosing chamber; during the machine operation, the programmer operates an actuator for releasing a discharge outlet in correspondence with the dosing chamber, to let the dosed amount of rinsing aid flow from the latter in the wash tub of the dishwasher.
As said, the above tank generally has enough capacity for containing a sufficient amount of liquid agent to perform several wash cycles; thus, the machine user will only have to fill the tank through the proper plug periodically.
Dispensers as above are usually fitted with means informing the user about the need of filling the above tank with the liquid washing agent.
To this purpose, more sophisticated solutions have the dispenser fitted with a proper electric or electronic sensor, which is capable of detecting the presence of a liquid washing agent inside the relevant tank; this sensor is appropriately connected to the machine control system, so that the latter, should no liquid washing agent be detected inside the tank, enables optical and/or acoustical means, such as a lamp or a buzzer.
This type of solution, though being quite efficient, involves a considerable increase in cost for the dispenser, due to the presence of the sensor; also the machine using such a dispenser generally has a higher cost, due to the need of appropriately connecting the sensor to the machine control system and the relevant signalling means.
Less sophisticated solutions, on the contrary, have the a simple visual device associated with the tank, for ascertaining the level of the liquid washing agent.
Typically, this visual device comprises a circular passage extending from the tank containing the liquid washing agent to the front surface of the dispenser body; a transparent element in plastic, such as polycarbonate or methacrylate, whose shape matches the passage itself, namely cylindrical, is at least partially inserted in this passage; indications about the amount of liquid washing agent contained in the relevant tank can be obtained through this transparent element.
A dispenser as described above is illustrated in FIG. 1 of DE-A-195 45 773.
In any event, other solutions are also known, wherein one same dispenser is fitted with both an electric/electronic level sensor and a simple visual signalling device, as mentioned above.
In the annexed FIG. 1A there are represented different views of a typical known embodiment of a transparent element as above indicated, indicated with 1 as a whole.
As it can be noticed, the transparent element 1 has a mainly cylindrical shape, showing an upper portion 1A and a lower portion 1B delimited between them by a substantially circular flange 2.
The upper portion 1A is entirely cylindrical and is provided for being inserted with interference in the relevant passage defined in the dispenser body; it should be noticed that a dispenser body usually consists of two parts welded to each other, whereby the portion 1A of the transparent element 1 is inserted before this welding operation in the relevant circular passage from the side opposite to the side that forms the front surface of the dispenser.
The portion 1A is inserted in the relevant passage until the flange 2 strikes against the inner surface of the dispenser body; as said above, this is done with interference and the portion 1A of the element 1 has a set of surface knurls 3, whose function is to avoid possible draining of the liquid washing agent outside the tank; following the above insertion, the front surface 4 of the portion 1A is flush with the front surface of the dispenser body.
The lower portion 1B of the transparent element 1, on the contrary, is provided to result in being inserted within the tank containing the liquid washing agent; as it can be noticed, a set of projections 5 is delimited on its lower end, each one having a substantial triangular or pentagonal prism form, arranged alongside like steps, i.e. laying at different heights.
The operation of such a visual signalling device is quite simple.
When the loading door of the dishwashing machine is in its open position, i.e. horizontal (which is also the typical loading position of the liquid washing agent in the relevant tank), the number of projections 5 immersed in the liquid washing agent is in function of the amount of the latter; in other words, the higher the washing agent level in its relevant tank, the higher the number of projections 5 immersed in it.
The transparent element 1 is actually manufactured so as to visually transmit, from the projections 5 to the front surface 4, an indication of the level of the liquid washing agent, which depends on the number of projections 5 in contact with the liquid washing agent; should the liquid washing agent be lacking either totally or partially, the surface 4 would visibly show horizontal lines indicating the length-wise limits of the projections 5 not immersed in the liquid washing agent, due to optical effect (see for instance the plan view of FIG. 1A); thus, the surface 4 acts as a graduated scale, whose subdivisions or steps are delimited by these horizontal lines.
Therefore, when the machine door is open (a condition that has to precede the start of a wash cycle), the user is able to check whether the liquid washing agent is available or not and/or its level.
To this purpose, let us consider a transparent element 1 fitted with four projections 5 and assume that the tank containing the liquid washing agent is filled to half its capacity.
In this situation, only the two projections 5 laying farther from the surface 4 (i.e. the first two projections 5 starting from the bottom with reference to FIG. 1A) will be immersed in the liquid washing agent. This situation corresponds to an intermediate level indication on the front surface 4 of the transparent element 1; in particular, the lower half of the front surface 4 will have a first color shade due to the optical effect produced by the projections 5 immersed in the fluid.
Vice-versa, the upper half of the surface 4 will have a lighter color shade, substantially matching the standard shade of the material forming the transparent element 1; a horizontal line will be visible due to optical effect on this second half in correspondence with the point of demarcation between the two projections 5 not immersed in the fluid.
The above described solution, though being simple and cheap, has some drawbacks.
As a first drawback, the “reading” the information obtainable from the signalling device according to the known technique is actually not very easy; rather, it is quite difficult, above all in the event of the liquid level in the relevant tank being at its minimum. Another drawback related to the common technique is due to the manufacture of the portion 1B of the transparent element 1, on which only a restricted number of projections 5 can be delimited; as a result, the user only has few indications and/or a low measurement resolution about the filling level of the tank with the liquid washing agent.
In order to clarify the above drawbacks, reference is made to the annexed FIG. 1B showing substantially the front surface 4 of the transparent element 1.
As it can be noticed, the subdivisions of the graduated scale consisting of the front surface 4 of the element 1 are visible; these subdivisions are represented by the parallel horizontal lines that, by optical effect, can be seen in correspondence with the demarcation points between the various projections 5.
The dimensions in the vertical direction (with reference to the figure) of each subdivision, and relevant projection 5, hereinafter referred to as step P, are the same for all the projections 5; the dimensions in the horizontal direction of the various subdivisions and relevant projections, hereinafter referred to as widths, are different, since the depend on the circular section of the portion 1B of the element 1; in particular, the two end projections and divisions (i.e. lower and upper ones) have a minor width with respect to the possible maximum one indicated with L, with respect to the two central subdivisions and projections.
Therefore, according to the type of realization of the prior art, the overall development S of the graduated scale given by the sum of individual steps P will never exceed the dimensions of minimum encumbrance, or width, of the surface 4 (in the specific case corresponding to diameter L of said surface), on which the various steps P have to be represented.
As it can be noticed, in order to ensure a satisfactory reading of the graduated subdivisions and an efficient interpretation of the associated level information, step P, i.e. the relevant dimension of the projection 5, should be sufficiently large; as said above, this implies a lower measurement resolution.
Apparently, in an attempt to solve the above drawback, step P (i.e. the relevant dimensions of the projections 5) might be reduced, maintaining the diameter of the portion 1B of the element 1 constant; thus, the graduated scale visible on the front surface 4 of the element 1 itself would have a higher number of subdivisions.
An increase of the measurement resolution so obtained would however lead to a firm worsening of the comprehensibility of the information which can be obtained from the signaling device: it is clear, in fact, that the lower is the step P of the subdivisions, the higher is their difficulty of interpretation.
On the other hand, theoretically, the increase of the number of projections 5, though maintaining an acceptable step P, could be possible only by increasing the diameter of the transparent element 1.
According to the prior art, however, the diameter of the section of the transparent element 1 should always be a reduced one; this requirement is also determined by the fact that, during the manufacturing stage, the element 1 is actually “hammered” in its relevant passage with a considerable mechanical interference between the parts, so as to obtain a safe position and above all ensure the necessary sealing.
Based on the above, it is quite clear that the larger the dimensions of the transparent element 1 are, the higher the force required during manufacture will be for its insertion and sealing in the relevant passage.
It should also be considered that the larger the dimensions of the transparent element 1 are (and consequently the force required for its insertion with a considerable interference in its relevant seat), the higher the failure risks of the components during manufacture will be. In other terms, since a considerable force has to be exerted on the transparent element to insert it inside a slightly tighter passage (to warrant a hydraulic sealing of mechanical type), there will be quite a high probability of breaking either the transparent element itself or the portion of dispenser body, wherein the passage is delimited.
Therefore, the transparent element 1 according to the prior art should have a reduced section for the above reasons.
This requirement, as mentioned above, cause a difficult “reading” of the information which can be ascertained from the signalling device; the consequent restricted number of projections 5 determines a poor indication and/or measurement resolution.